DRUM Community: Geologyhttp://hdl.handle.net/1903/2243
Wed, 04 Mar 2015 00:10:14 GMT2015-03-04T00:10:14ZLithium and its isotopes as a tracer of fluid flow mechanisms in the Catalina Schist melange zonehttp://hdl.handle.net/1903/16156
Title: Lithium and its isotopes as a tracer of fluid flow mechanisms in the Catalina Schist melange zone
Authors: Roble, Leigh Anne
Abstract: Mélange zones are areas of highly mixed and deformed rock believed to form from shearing between subducting slab and peridotite mantle wedge. They have high -pressure/low-temperature mineral assemblages and contain a fine-grained matrix with centimeter to meter scale blocks surrounded by rinds, thought to represent a reaction zone between the block and matrix. These rinds are not well understood, but could be formed due to mechanical mixing, diffusion, or infiltration. Lithium is used to determine the role played by fluid-mediated processes in the Catalina Schist mélange zone because it is fluid mobile and has high diffusivity. Samples from amphibolite, lawsonite-blueschist, and lawsonite-albite facies were retrieved from the Catalina Schist subduction complex on Santa Catalina Island. Lithium isotopic compositions and concentrations were determined using mass spectrometry techniques. One-dimensional diffusion models were applied to the data to determine the extent of the different mechanisms responsible for fluid transport throughout the subduction complex.Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/1903/161562014-01-01T00:00:00ZAnatexis and crustal differentiation: Insights from the Fosdick migmatite-granite complex, West Antarcticahttp://hdl.handle.net/1903/15755
Title: Anatexis and crustal differentiation: Insights from the Fosdick migmatite-granite complex, West Antarctica
Authors: Yakymchuk, Christopher
Abstract: In the Fosdick migmatite-granite complex of West Antarctica, U-Pb geochronology of monazite in migmatites and zircon in granites records two episodes of high-temperature metamorphism, one in the Devonian-Carboniferous and another in the Cretaceous. For the older lower-grade event, whole-rock and zircon isotope geochemistry of granites within the Fosdick complex are interpreted to record crustal reworking during metamorphism associated with continental arc magmatism along the East Gondwana convergent plate margin. By contrast, the geochemistry of correlative granites suites from along and across the same margin indicates a greater proportion of crustal growth. This suggests prominent arc-parallel and arc-normal variations in the mechanisms of crustal reworking versus growth in continental arc systems.
Based on garnet Lu-Hf ages, the timing of peak metamorphism in the younger higher-grade event has been determined as c. 116-111 Ma. U-Pb ages of monazite from migmatites and zircon from anatectic granites suggest that exhumation of the complex as a gneiss dome occurred during the interval c. 107-100 Ma. Contemporaneous exhumation of high-grade metamorphic rocks in the Western Province of New Zealand suggests that intracontinental extension preceded the final breakup of New Zealand from West Antarctica by c. 25 Myr.
Melt migration through and emplacement within the Fosdick complex during Cretaceous metamorphism was accomplished via a self-organized melt network controlled by the regional stress field and anisotropy of the host rocks. Granites within this network and in sills at shallower crustal levels have microstructures and chemistry consistent with a cumulate origin, and are interpreted to record fractional crystallization during magma ascent and doming related to exhumation.
Phase equilibria modeling of open system melting during prograde metamorphism is used to quantify the reduced fertility of source rocks during high-temperature exhumation and later overprinting orogenic events. Quantitative modelling of the dissolution of zircon and monazite during prograde melting demonstrates that accessory minerals are expected to be partially to completely consumed up to the metamorphic peak. New growth of these minerals in migmatite melanosomes is predicted to be limited during cooling, whereas leucosomes and anatectic granites are predicted to contain new zircon and monazite growth.Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/1903/157552014-01-01T00:00:00ZVegetation-Hydrodynamic Interactions and the Stability of Channel Inlets of Tidal Freshwater Wetlands, Chesapeake Bay Systemhttp://hdl.handle.net/1903/15751
Title: Vegetation-Hydrodynamic Interactions and the Stability of Channel Inlets of Tidal Freshwater Wetlands, Chesapeake Bay System
Authors: Statkiewicz, Anna
Abstract: To maintain elevation, deposition of mineral and organic sediment in tidal freshwater wetlands (TFWs) must outweigh losses due to sea-level rise, erosion, decomposition, and compaction. Sediment loads into tidal marshes are controlled by inlet size and sediment supply, but interactions among vegetation, hydraulics, and geomorphology affect sediment retention. This study focused on these interactions in TFW inlets partially covered by aquatic vegetation (N.luteum, Z.aquatica, and H.verticullata). Measurements of hydraulic parameters and geomorphic change were correlated with observations of spatial and morphological characteristics for each vegetation type. The aquatic plants grew in significantly different water depths and well-defined platforms formed in areas occupied by emergent vegetation where effective shear stress is lowest. Net annual accretion data indicate an inverse relationship between maximum inlet depth and accretion rate. These results suggest that initial vegetation colonization modifies channel inlet morphology; both vegetation and morphology generate the shear stress distributions, which maintain channel form.Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/1903/157512014-01-01T00:00:00ZSupercritical Fluid Extraction of Hydrocarbons from the Marcellus Shale by Using CO2http://hdl.handle.net/1903/15706
Title: Supercritical Fluid Extraction of Hydrocarbons from the Marcellus Shale by Using CO2
Authors: Jarboe, Palma Jean
Abstract: Supercritical carbon dioxide was used to extract n-aliphatic hydrocarbons from samples of Marcellus shale, and to evaluate recovery as a function of sample matrix particle size (sieve size). Results show that supercritical CO2 has the potential to liberate diesel-range n-aliphatic hydrocarbons from high-maturity shale at estimated in situ pressure and temperature conditions. Total quantity of resolvable n-aliphatic hydrocarbons ranged from approximately 0.3 - 12 milligrams of hydrocarbon per gram of total organic carbon. No significant differences in extracted hydrocarbons were observed between crushed samples of different sieve sizes (1000 - 500 µm, 250 - 125 µm, and 63 - 25 µm). However, some increase in hydrocarbon extraction efficiency was seen as a function of exposed surface area. Additionally, a slight positive correlation was also observed between hydrocarbon recovery and S1 (free oil content) warranting further investigation.Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/1903/157062014-01-01T00:00:00Z